WANG Zhaoyin and ZHANG Chendi

Abstract: The continuous uplifting of Qinghai-Tibet Plateau results in the river incision on the margin of Qinghai-Tibet plateu. River incision leads to frequent disasters such as bank failures, avalanches, landslides and debris flows. Based on the field investigations and experiments over the past decade, it is found that natural dams, which are formed after landslides or debris flows block the channel, perform as the negative feedback to river incision. The natural dams are capable to control erosion and incision efficiently, stabilize the riverbed and improve the local ecology. The functions above stem from the bedforms developed on natural dams. The present paper summarizes the mechanism of bedforms and natural dams on energy dissipation and disaster mitigation. The quantification of energy dissipation rate of step-pool, which stands for bedforms, has been put forward. Furthermore, the concept and logic of energy budget in the integrated management of incised rivers is demonstrated in the present paper. The successful application of artificial step-pool system in a debris flow gully is introduced, to illustrate the feasibility and efficiency of artificial energy dissipaters mimicking natural dams in disaster prevention and mitigation. Last but not least, based on the idea of energy dissipation, we suggest that the successive reservoir-dam system consisting of medium-sized dams should be applied in the development and management of the incised river in southwest China, to realize the comprehensive objective including dissipating flow energy, stabilizing the riverbed and promoting the ecology.

Keywords: natural dam; bedform; energy dissipation and disaster mitigation; barrier dam; step-pool system system